REVIEW
Wilson Loops in the Large N Limit at Finite Temperature
High Energy Physics - Theory · Submitted 17 Mar 1998 · 34 references
Pith's verdict: The paper that first put a heavy quark pair in the N=4 plasma and got thermal screening out of it; the computation is clean and the qualitative answer has held up.
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Referee report
The paper
The paper claims
A quark and its antiparticle, held in a hot strongly coupled plasma, feel a Coulomb force at short range and essentially no force at all once their separation exceeds a distance set by the inverse temperature.
The reading
What carries the argument
The machinery is the Nambu-Goto action of a string in the near-extremal D3-brane metric, $ds^2 = (U^2/R^2)(-f(U)dt^2 + dx_i^2) + R^2 f(U)^{-1} dU^2/U^2 + R^2 dOmega_5^2$ with $f(U)=1-U_T^4/U^4$, together with the conserved 'Hamiltonian' in the $x$ direction that follows from translation invariance, $ (U^4-U_T^4)/sqrt((partial_x U)^2 + (U^4-U_T^4)/R^4) = R^2/sqrt(U_0^4-U_T^4)$. That constant of motion converts the problem into two quadratures: one relating the turning point $U_0$ to $L$ through the parameter $epsilon = 1 - U_T^4/U_0^4$, and one giving the energy after subtracting the mass of a straight string running from the boundary to the horizon. The horizon endpoint is what makes the subtraction finite and is therefore the load-bearing structural choice of the whole calculation.
Extended reading notes
Core claim
The authors take the near-extremal D3-brane supergravity solution — a black hole in the five-dimensional geometry dual to the four-dimensional gauge theory at temperature $T$ — and put a Nambu-Goto string in it, with the string's two ends on the boundary representing the quark and antiquark. Because the metric does not depend on the spatial coordinate along the pair, the string action has a conserved quantity, and the turning point $U_0$ of the hanging string is related to the separation $L$ by a single integral; the static energy is a second integral over the same variable. The new ingredient relative to the zero-temperature treatment is where the string is allowed to end: the authors argue that in the presence of a horizon the string terminates at $U=U_T$, not at $U=0$, and it is this choice that makes the mass subtraction finite. Eliminating $U_0$ between the two integrals gives a curve with a maximum separation $L_{max}$ and, before that maximum is reached, a critical separation $L_C$ at which the connected string's energy equals that of two independent straight strings. Beyond $L_C$ the connected configuration is no longer the lowest-energy one, so the physically relevant answer is two free quarks with no force between them. The resulting picture is a Coulomb-like energy $E=-2^{3/2}(4g^2_{YM}N)^{1/2}/(4^{1/4}L)$ at small $TL$, corrected by a positive constant times $(TL)^4$, and vanishing energy at large $TL$.
Load-bearing premise
The whole finite answer rests on the claim that the string dual to a heavy quark ends on the black-hole horizon rather than at the singularity, a choice the authors support with three qualitative arguments — a coordinate transformation, the fact that the Euclidean continuation covers only the exterior, and a Hawking-radiation burning estimate — rather than a derivation, and a different endpoint would change the subtraction and with it the entire energy curve.
Editorial extensions
If this is right
- For separations much smaller than $1/T$ the quark-antiquark energy stays Coulomb-like, $E \sim -1/L$, with a correction of relative size $(TL)^4$; the combination $EL$ can depend on temperature only through $TL$, which is the theory's conformal symmetry showing itself.
- For separations of order $1/T$ and beyond, the energy goes to zero: the thermal bath screens the pair, and two isolated free quarks become the energetically preferred configuration.
- Because the connected string stops being the ground state at $L_C$, the calculation should be trusted only up to $L_C$, which lies below the maximum separation $L_{max}$ that the parametric curve would otherwise allow; the apparent double-valued region is unphysical.
- On non-compact space a conformal theory has no phase transition at finite temperature, only a crossover; a transition can appear only when some scale, such as the radius of a sphere the theory lives on, breaks conformal invariance.
- The same supergravity prescription should extend to non-conformal theories with sixteen supercharges, where a length scale is present and genuine phase transitions become possible.
Reading between the lines
- The screening length extracted here, $L_C T$ of order one, is a strong-coupling prediction that has no weak-coupling analogue; comparing its precise numerical value against resummed perturbative or lattice treatments of the same theory would be the sharpest test of the duality in a thermal setting.
- The paper's subtraction scheme effectively treats the horizon as the floor of the geometry rather than the singularity, which suggests that the correct field-theory interpretation of the interior region is that it is simply absent from the gauge theory's description, not merely hard to access.
- Because the energy vanishes smoothly rather than jumping, the crossover resembles Debye screening in an ordinary plasma; it would be natural to ask whether a screening mass can be read off the long-distance behaviour of the finite-temperature Wilson loop and matched to a thermal mass computed independently.
- The result is stated for infinitely heavy external quarks; a finite-mass quark would introduce a string that can break, and the crossover to free quarks might then be softened or shifted, which is a computable extension within the same setup.
Original abstract
Using a proposal of Maldacena we compute in the framework of the supergravity description of N coincident D3 branes the energy of a quark anti-quark pair in the large N limit of U(N) N=4 SYM in four dimensions at finite temperature.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
Using a proposal of Maldacena we compute in the framework of the supergravity description of N coincident D3 branes the energy of a quark anti-quark pair in the large N limit of U(N) N=4 SYM in four dimensions at finite temperature.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Using a proposal of Maldacena we compute in the framework of the supergravity description of N coincident D3 branes the energy of a quark anti-quark pair in the large N limit of U(N) N=4 SYM in four dimensions at finite temperature. | contribution 0.98 | 0.94 | 0.24 | asserted 0.99 |
What was examined, and what was not
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Figures
Showing 3 of the paper's 5 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:hep-th/9803137 by the authors.
References
How later papers used it
73 later papers cite it
4 later papers by other authors are listed below: 3 used its method or tool and 1 compared its own results with it.
Uses its method or tool 3 of 7 papers with this label
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Used the same boundary conditions for each string configuration and the U-shaped profile of the string in the bulk from this paper.
Anisotropic heavy quark potential in strongly-coupled $\mathcal{N}=4$ SYM in a magnetic field (2014) · 0.88 · paraphrased: the licence does not allow quoting
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Used the second contribution on the r.h.s. of this paper as the required counter-term subtracting the very massive quark and antiquark contributions to the regularized potential.
Hadron potentials within the gauge/string correspondence (2008) · 0.88 · paraphrased: the licence does not allow quoting
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Subtracted the self-energy corresponding to two disconnected strings hanging from ϵ to r_h, as in this paper, to remove the regulator for the Polyakov-loop correlator in AdS.
Gravity/Spin-model correspondence and holographic superfluids (2010) · 0.84 · paraphrased: the licence does not allow quoting
Compares with it 1 of 10 papers with this label
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Compared its own results for the potential in the Schwarzschild-AdS_5 background with this paper's V_qq̅ in the planar AdS black hole.
Probing the holographic model of $\mathcal{N} =4$ SYM rotating quark-gluon plasma (2022) · 1.00 · paraphrased: the licence does not allow quoting
How the literature uses it
70 arXiv papers cite this in 121 sentences
Papers citing it · 65 sentences without a confident label
Builds on it 1 paper
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Then we propose the mass renormalization scheme generalizing the static case idea [ref] .
Holographic Non-local Rotating Observables and their Renormalization · Introduction · 0.92
Uses its method or tool 6 papers
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In [ref] , we computed $⟨W_0⟩$ in both extremal and non-extremal geometries following the procedure of [ref] - [ref] .
Non extremal geometries and holographic phase transitions · Phase Transitions · 0.89
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We follow the holographic prescription proposed in [ref] (see also [ref] and references therein for more recent discussions) to evaluate the rectangular loops in SYM in the strong t'Hooft coupling limit, $λ≫1$, with a large number of colors, $N →∞$, in terms of a classical Nambu-Goto action in the background discussed in the previous section.
Anisotropic heavy quark potential in strongly-coupled $\mathcal{N}=4$ SYM in a magnetic field · Holographic Wilson loop $∥ℬ̌$ at $T=0$ · 1.00
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The second contribution on the r.h.s. of [ref] is the required counter-term which subtracts the very massive quark and antiquark contributions to the regularized potential and which takes in this case the following form ($ℓ=2r+2TT≫r≃2T$ and $M=U_max-U_T/2π$): [equation] Indeed, the "W-boson string" corresponds here to an open string stretched between the brane at $U_max$ and the Schwarzschild horizon $U=U_T$ [ref] .
Hadron potentials within the gauge/string correspondence · The conformal behaviour of the Wilson loop at finite temperature · 0.88
Compares with it 9 papers
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In the phase diagram of SYM theory, our new result can be interpreted as deforming the superconformal $𝒩=4$ SYM theory by finite chemical potential, in contrast to the finite-temperature deformation considered in [ref] .
Quantum-Corrected Holographic Wilson Loop Expectation Values and Super-Yang-Mills Confinement · Introduction · 0.89
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This matches with the result found in Refs. [ref] using the extremal F-string probe in the $$ Poincaré black hole background. $LT$ also exhibits a maximum in this case: Its value is $L_max T ≃0.277$ and it is reached for $σ̂_0 ≃0.85$.
Thermal string probes in AdS and finite temperature Wilson loops · Finite $LT$ and Debye screening of charges · 0.88
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In Fig. [ref] we compare our results for the potential in the Schwarzschild-$AdS_5$ background with $V_qq̅$ in the planar AdS black hole [ref] .
Probing the holographic model of $\mathcal{N} =4$ SYM rotating quark-gluon plasma · Wilson loop in Schwarzschild-$AdS_5$ black hole · 1.00
Cites it as background 32 papers
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The potential for static heavy quarkonia at finite temperature in $𝒩=4$ super Yang-Mills theory was calculated via the methods of AdS/CFT by [ref] .
Bottomonia Suppression in Heavy Ion Collisions from AdS/CFT · Introduction · 0.95
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The polygon taken as an example is a lightlike version of the usual contour taken in the calculation of $V_qq̅(L)$ through the Wilson loop [ref] , which boosted gives the contour used for the jet-quenching parameter calculation [ref] .
Gluon scattering in ${\cal N}=4$ Super Yang-Mills at finite temperature · Introduction · 0.84
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The calculation of the free energy of a static pair in an $𝒩=4$ SYM plasma [ref] was among the first applications of the AdS/CFT correspondence.
Free Energy of a Heavy Quark-Antiquark Pair in a Thermal Medium from AdS/CFT · Introduction · 0.97
Discussion
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